National Find a Rainbow Day
Friday, April 3, 2026
From reflection to refraction. Aristotleproposed around350 BCEthat rainbows resulted from the reflection of sunlight off clouds. The explanation was wrong, but it stood largely unchallenged for over 1,500 years. The first real breakthrough came in1304, when. Theodoric of Freiberg, a Dominican friar, filled glass spheres with water and traced the path of light through them. He showed that light refracts when entering a water droplet, reflects off the inner surface, and refracts again on the way out.Rene Descartesbuilt on Theodoric's work in1637, publishing a mathematical proof that light exits a raindrop at approximately42 degreesrelative to the incoming ray. This explained the consistent angular size of rainbows but left one question unanswered: why the colors
History
From reflection to refraction. Aristotleproposed around350 BCEthat rainbows resulted from the reflection of sunlight off clouds. The explanation was wrong, but it stood largely unchallenged for over 1,500 years. The first real breakthrough came in1304, when. Theodoric of Freiberg, a Dominican friar, filled glass spheres with water and traced the path of light through them. He showed that light refracts when entering a water droplet, reflects off the inner surface, and refracts again on the way out.Rene Descartesbuilt on Theodoric's work in1637, publishing a mathematical proof that light exits a raindrop at approximately42 degreesrelative to the incoming ray. This explained the consistent angular size of rainbows but left one question unanswered: why the colors
How It's Celebrated
National Find a Rainbow Day is observed by recognizing the importance of the day, learning about its background and significance, and sharing awareness with others through conversation and social media. Many people take time to reflect on the meaning of the observance and participate in relevant activities or community events.